We've had lots of requests for these 1B1B6 engraved mil spec / mil contract 1B1B6 carriers specifically. Toolcraft assembles the 1B1B6 carrier to a mil-spec Carpenter 158 bolt to make a complete Mil-Spec BCG kit. The 1B1B6 carriers are hard to get, so we've had to price them a little higher than our regular Toolcraft black BCG's. They're both the same, high quality.